Growth And Characterization Of Wide Gap II-VI Heterostructures

At this time there is evident a sharp increase of interest in the II-VI class of semiconducting compounds largely due to recent success in the growth of these materials by molecular beam epitaxy (MBE). One of the more important areas for application of high quality II-VI films is infrared imaging where CdTe deposited by MBE onto GaAs substrates is proposed as the substrate for subsequent HgCdTe and HgTe/CdTe superlattice deposition. Moreover, interest in the widegap II-VI compounds is stimulated by the need for electronically addressable flat panel display devices, and for the development of wide gap (blue) LED and injection laser devices. For applications in the blue portion of the visible spec-trum, ZnSe and ZnS have long been favored candidates. Very high quality ZnSe has recently been grown by MBE. The photoluminescence spectra of the MBE-grown ZnSe samples grown at Purdue and elsewhere strongly suggests that, in many cases, the film quality exceeds that obtainable in bulk form. In addition to the conventional II-VI materials, a new class of materials called diluted magnetic semiconductors (DMS) are currently receiving considerable attention. DMS are II-VI semiconductors such as CdTe or ZnSe with a fraction of the group II element substituted by a magnetic transition element such as Mn. The incorporation of Mn leads to very large magneto-optic effects, of the order of several hundred times that exhibited by conventional semiconductors of comparable bandgap. An especially significant feature of II-VI DMS materials is the increase in bandgap resulting from Mn incorporation. The bandgap increases with Mn mole fraction in a manner similar to the effect of Al in the (Ga,A1)As system, and with similar implications to the creation of quantum well structures and superlattices.